Collaborative Research: The Effect of Variations in Cloud Versus CO2 Radiative Forcing on Tropical SST Gradients, Atmospheric Circulation and Rainfall Patterns

合作研究：云与二氧化碳辐射强迫的变化对热带海温梯度、大气环流和降雨模式的影响

• 批准号: 1613318
• 负责人: Natalie Burls
• 金额: $ 26.73万
• 依托单位: George Mason University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-15 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1613318&HistoricalAwards=false
• 关键词: Collaborative; Research; Effect; Variations; Cloud

Simulations of the response of tropical climate to greenhouse gas increases show a prominent role for clouds in determining how much the tropics warm, how the warming is distributed geographically, and how it affects other aspects of the climate. Many aspects of tropical climate, including the distribution of rainfall and surface winds, are closely related to the east-west sea surface temperature (SST) gradient along the equatorial Pacific, between the warm pool of the western Pacific and the cold tongue extending from the eastern boundary. Previous work by the PIs shows a strong relationship between the SST gradient in the equatorial Pacific and the contrast in brightness, or albedo, between tropical and extratropical clouds. The PIs have developed a theory to explain this connection, in which extratropical clouds with higher albedo imply less sunlight absorbed by the ocean at higher latitudes, which in turn requires greater heat transport from the tropics, which is satisfied by greater oceanic heat uptake in the cold tongue and subsequent oceanic transport, which requires colder temperatures in the cold tongue and thus a greater temperature contrast between the cold tongue and the warm pool.Motivated by this theoretical framework, the PIs test the hypothesis that latitudinal variations in the response of cloud albedo to greenhouse warming play a key role in driving changes in tropical climate associated with the east-west SST contrast across the Pacific. The PIs perform greenhouse warming simulations with the Community Earth System Model (CESM) in n fully coupled, slab ocean, and prescribed SST configurations, in which cloud feedbacks and their effects on the equatorial Pacific SST contrast are assessed. Complimentary analysis of greenhouse warming simulations from the archive of the Coupled Model Intercomparison Project version 5 (CMIP5) is also performed. As ocean heat transport plays an important role, a water parcel tracking scheme is applied to identify the location and time of last ventilation for water in the equatorial mixed layer, which can then be related to cloud radiative effects felt by the parcel during ventilation.The research has broader societal impacts as it addresses fundamental issues in tropical climate which are essential for anticipating future climate changes in a populous region. The work has broader scientific impacts because the results will likely be helpful for understanding warm climates of the past, in particular the Pliocene, a period 3-5 million years ago when carbon dioxide levels were as high as today and the equatorial Pacific SST gradient is believed to have been weaker. The work has additional educational broader impacts through the participation of one of the PIs in National Center for Science Education "Scientists in the Classroom" pilot project, in which she will work with a middle school teachers and students. In addition, the project provides support and training to a graduate student and a postdoc, thereby providing for the future workforce in this research area.

模拟热带气候对温室气体增加的响应表明，云在确定热带变暖程度、变暖在地理上的分布以及它如何影响气候的其他方面方面起着重要作用。 热带气候的许多方面，包括降雨和地面风的分布，都与沿赤道太平洋沿着、西太平洋暖池和从东边界延伸的冷舌之间的东西向海表温度（SST）梯度密切相关。 PI先前的工作表明，赤道太平洋的SST梯度与热带和热带外云层之间的亮度对比（或亮度对比）之间存在很强的关系。 PI已经开发了一种理论来解释这种联系，其中具有较高湿度的热带云确实意味着较高纬度的海洋吸收较少的阳光，这反过来又需要来自热带的更多热量传输，这通过冷舌中更多的海洋热量吸收和随后的海洋传输来满足，这就要求冷舌的温度更低，因此冷舌和暖池之间的温度差异更大。受这一理论框架的启发，PI检验了这样一个假设，即云的纬度变化对温室效应的响应在驱动与太平洋东西SST对比相关的热带气候变化方面起着关键作用。 PI执行温室效应变暖模拟与社区地球系统模式（CESM）在n完全耦合，板状海洋，和规定的SST配置，云反馈及其对赤道太平洋SST对比度的影响进行了评估。 还对耦合模式相互比较项目第5版（CMIP 5）的档案中的温室变暖模拟进行了补充分析。 由于海洋热传输起着重要的作用，水包裹跟踪计划被应用到确定的位置和时间的最后通风的水在赤道混合层，这可以与云辐射的影响感到包裹在ventilation.The研究有更广泛的社会影响，因为它解决了热带气候的基本问题，这是必不可少的预测未来的气候变化在人口稠密的地区。 这项工作具有更广泛的科学影响，因为其结果可能有助于了解过去的温暖气候，特别是上新世，这是300万至500万年前的一个时期，当时二氧化碳水平与今天一样高，赤道太平洋SST梯度被认为较弱。 这项工作有额外的教育更广泛的影响，通过参与国家科学教育中心的PI之一“科学家在课堂上”试点项目，在该项目中，她将与一所中学的教师和学生。 此外，该项目还为一名研究生和一名博士后提供支持和培训，从而为这一研究领域的未来劳动力提供支持。